| Longnes | |
| Commune Status: | Commune |
| Arrondissement: | Mantes-la-Jolie |
| Canton: | Bonnières-sur-Seine |
| Insee: | 78346 |
| Postal Code: | 78980 |
| Mayor: | Anne Debras[1] |
| Term: | 2023 - 2026 |
| Intercommunality: | Pays houdanais |
| Coordinates: | 48.9217°N 1.5881°W |
| Elevation M: | 125 |
| Elevation Min M: | 109 |
| Elevation Max M: | 160 |
| Area Km2: | 13.76 |
Longnes is a commune in the Yvelines department in the Île-de-France region in north-central France.